Brachytherapy involves the placement of low-dose radiation sources in a pre-determined pattern within a tumor, and has been found to be an accepted alternative to general surgery for the treatment of cancer, particularly for the treatment of prostate cancer. Langely et al. “Prostate brachytherapy has come of age: a review of the technique and results” R. BJU Int'l., 89, 241–249 (2002).
The low-dose sources (known as “radioactive sources”, “implants”, “brachytherapy seeds”, or simply “seeds”) typically have an outer shell made of a biocompatible material, such as titanium, that encapsulates a radioactive source (typically 0.1–2.0 mCi of either 125I or 103Pd). Commercially available seeds include Symmetra® I-125 (Bebig GmbH, Germany); Iogold™I-125 and Iogold™ Pd-103 (North American Scientific, Inc., Chatsworth, Calif.); Best® I-125 and Best® Pd-103 (Best Industries, Springfield, Va.); Brachyseed® I-125 (Draximage, Inc., Canada); Intersource® Pd-103 (International Brachytherapy, Belgium); Oncoseed®I-125 (Nycomed Amersham, UK); STM 1250 I-125 (Sourcetech Medical, Carol Stream, Ill.); Pharmaseed®I-125 (Syncor, Woodland Hills, Calif.); Prostaseed™ I-125 (Urocor, Oklahoma City, Okla.); I-plant® I-125 (Implant Sciences Corporation, Wakefield, Mass.); Advantage™ I-125 IsoAid Inc. (Port Richey, Fla.); TheraSeed® Pd-103 (Theragenics, Buford, Ga.); Prospera® Pd-103 (North American Scientific, Inc.); and IsoSeed® I-125 (Isotope Products Laboratories (IPL), Valencia, Calif.). The seeds typically are sized to fit down the lumen of a brachytherapy needle. Most such needles are about 18 gauge, and the seeds typically have a diameter of about 0.8 mm and a length of about 4.4 mm.
The seeds preferably are placed within a tumor in a pattern that provides a maximum, cytotoxic dose to the cancerous cells but leaves normal tissue unaffected. Biodegradable, biocompatible spacers can be positioned between the seeds to maintain a desired spacing. Implantation of the seeds and spacers typically is achieved by loading them in a generally linear fashion into a needle and inserting the loaded needle into the tumor. A long stylet is then inserted into the proximal end of the needle and positioned against the terminal seed or spacer. The needle is then removed from the tumor, leaving the seeds and spacers essentially in place.
Brachytherapy seeds are commonly shipped in a non-sterile state in a glass vial. Upon receipt, hospital personnel sterilize the seeds and a radiation physicist loads them, along with spacers, into the lumen of a pre-plugged needle. This is a tedious task involving a significant radiation dose to the physicist performing the loading, and potentially to the hospital personnel in charge of sterilization.
U.S. Pat. No. 6,554,760 discloses one alternative to shipping non-sterile brachytherapy seeds. In particular, the patent discloses an assembly in which the seeds are pre-loaded into a needle and sterilized at the factory. Upon delivery to the hospital, the assembly is then ready for use without need for further sterilization.
U.S. Pat. No. 6,530,875 discloses a brachytherapy seed deployment system in which sterilized seeds and spacers are pre-loaded into a transparent tubular sleeve at the factory. The sleeve is inserted into a needle designed to receive the sleeve, and the needle/sleeve composite structure is used in an implantation procedure.
A need still exists for alternative ways to provide pre-sterilized seeds and spacers in a format that allows for facile loading into a variety of the different types of needles used for brachytherapy, and also allows for ready verification of the loading pattern and activity.